Method for calculating compensation value

ABSTRACT

A method for calculating a compensation value for use in a correction of a liquid landing position in a liquid ejection device provided with a first head for ejecting a first colored liquid and a second head for ejecting a transparent liquid includes, when forming a test pattern on a medium, forming the test pattern by feeding the first colored liquid to the second head and causing the second head to eject the first colored liquid, and obtaining a compensation value for a correction of a landing position of a liquid ejected by the second head on the basis of the test pattern formed on the medium.

BACKGROUND

1. Technical Field

The present invention relates to a method for calculating a compensationvalue.

2. Related Art

Ink jet type printers which form images by ejecting ink have beendeveloped. In such an ink jet type printer, in order to compensatelanding position errors of ink, a series of measures of performingprinting of a test pattern, reading in this test pattern by using ascanner, detecting landing errors, and performing control of ejectiontiming points on the basis of the detected landing errors have beenimplemented.

In JP-A-2004-338275, there is disclosed a method of performing a testprint, reading in an image of this test print and correcting landingpositions of ink on the basis of the read-in image.

Such ink jet type printers include ones which are of a type providedwith a function of ejecting a clear ink. In this case, however, it isdifficult for a scanner to exactly read in landing positions of theclear ink because the clear ink is transparent. For this reason, just anapplication of such a landing position correction method described abovehas been insufficient to enable correction of landing positionmisalignments with respect to the clear ink. Accordingly, even in thecase where a transparent ink is ejected, a method of appropriatelycorrecting landing positions thereof is desired.

SUMMARY

An advantage of some aspects of the invention is to provide a method of,even in the case where a transparent liquid is ejected, correctinglanding positions thereof appropriately.

According to an aspect of the invention, there is provided a method forcalculating a compensation value for use in a correction of a liquidlanding position in a liquid ejection device provided with a first headfor ejecting a first colored liquid and a second head for ejecting atransparent liquid. The method includes, when forming a test pattern ona medium, forming the test pattern by feeding the first colored liquidto the second head and causing the second head to eject the firstcolored liquid, and obtaining a compensation value for a correction of alanding position of a liquid ejected by the second head on the basis ofthe test pattern formed on the medium.

Other aspects of the invention will become apparent from description ofthis specification and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram illustrating the whole configuration of aprinter.

FIG. 2 is a schematic side view of a printer.

FIG. 3 is an explanatory diagram of an arrangement of heads in each ofhead units which is associated with a corresponding one of ink colors.

FIG. 4 is a flowchart illustrating a compensation value calculationmethod for a clear head.

FIG. 5 is an explanatory diagram of inks with each of which acorresponding one of head units is filled.

FIG. 6A is a first explanatory diagram of ink feeding paths, and FIG. 6Bis a second explanatory diagram of ink feeding paths.

FIG. 7 is a schematic explanatory diagram of a test pattern.

FIG. 8 is a first explanatory diagram of a test pattern.

FIG. 9 is an explanatory diagram of an error of a ruled line printed bya clear head.

FIG. 10 is a second explanatory diagram of a test pattern.

FIG. 11 is a flowchart illustrating printing processing.

FIG. 12 is an explanatory diagram of pixel data shifting processing.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

At least the following matters will become apparent from description ofthis specification and the accompanying drawings. That is, a method forcalculating a compensation value for use in a correction of a liquidlanding position in a liquid ejection device provided with a first headfor ejecting a colored liquid and a second head for ejecting atransparent liquid includes, when forming a test pattern on a medium,forming the test pattern by feeding the colored liquid to the secondhead and causing the second head to eject the colored liquid, andobtaining a compensation value for a correction of a landing position ofa liquid ejected by the second head on the basis of the test patternformed on the medium.

Through this method, when a test pattern is formed, a colored liquid isfed to the second head for ejecting a transparent liquid, and thus, thesecond head can form the test pattern by using the colored liquid.Further, on the basis of the test pattern having been formed by usingthe colored liquid, it becomes possible to obtain a compensation valuefor a correction of a landing position of a liquid ejected by the secondhead. In this way, a compensation value for the second head which ejectsa transparent liquid can be obtained, and thus, it becomes possible toappropriately correct a landing position of the transparent liquidejected by the second head.

In the aforementioned method for calculating a compensation value,preferably, the liquid ejection device is provided with a third head forejecting a white liquid, and when the test pattern is formed, the testpattern is formed by feeding a second colored liquid to the third headand causing the third head to eject the second colored liquid and acompensation value for a correction of a landing position of a liquidejected by the third head is obtained on the basis of the test patternformed on the medium.

Through this method, when a test pattern is formed, a colored liquid isfed to the third head for ejecting a white liquid, and thus, the thirdhead can form the test pattern by using the colored liquid. Further, onthe basis of the test pattern having been formed by using the coloredliquid, it becomes possible to obtain a compensation value for acorrection of a landing position of a liquid ejected by the third head.In this way, a compensation value for the third head which ejects awhite liquid can be obtained, and thus, it becomes possible toappropriately correct a landing position of the white liquid ejected bythe third head.

Further, preferably, when the test patter is formed, a color of thefirst colored liquid fed to the second head is different from a color ofthe second colored liquid fed to the third head.

In this way, when a test pattern is formed, the second head can be fedwith a color the same as a color of a head adjacent to the second head,and the third head can be fed with a color the same as a color of a headadjacent to the third head. For example, in the case where a headadjacent to the second head ejects a yellow liquid, the second head canbe fed with the yellow liquid, and simultaneously therewith, in the casewhere a head adjacent to the third head ejects a cyan liquid, the thirdhead can be fed with the cyan liquid.

Further, preferably, the liquid ejection device is provided with a firstcontainer for storing therein the first colored liquid and a first flowpath for feeding the first colored liquid to the second head from thefirst container, as well as a second container for storing therein thetransparent liquid and a second flow path for feeding the transparentliquid to the second head from the second container, and, when the firstcolored liquid is fed to the second head, the first colored liquid isfed to the second head through the first flow path, and feeding of thetransparent liquid to the second head through the second flow path isbrought to a stop.

In this way, it becomes possible to feed a colored liquid to the secondhead by controlling the feedings of liquids through the first and secondflow paths to the second head.

Further, preferably, the liquid ejection device is provided with afourth head for ejecting a colored liquid whose color is different froma color of the first colored liquid, and when the test pattern isformed, the fourth head is caused to form a first pattern, the secondhead is caused to form a second pattern, and a compensation value for acorrection of a landing position of a liquid ejected by the second headis obtained on the basis of the first pattern and the second pattern.

In this way, it becomes possible to obtain a compensation value for acorrection of a landing position of a liquid ejected by the second headin a relation between the first pattern formed by the fourth head andthe second pattern formed by the second head.

Further, preferably, the liquid ejection device is provided with aplurality of the second heads; the plurality of second heads arearranged such that a nozzle row of any one of the second heads extendsso as to overlap at least part of a nozzle row of at least one of theother ones of the second heads in a direction intersecting with adirection in which the medium is transported; and a compensation valuefor a correction of a landing position of a liquid ejected by any one ofthe second heads is equivalent to a compensation value which is obtainedsuch that, for any two ones of the second heads, a landing position of aliquid ejected by one of the two ones of the second heads is made abaseline, and on the basis of the baseline, a compensation value for acorrection of a landing position of a liquid ejected by the other one ofthe two ones of the second heads is obtained.

In this way, it becomes possible to, for a pair of the second headswhich are adjacent to each other, make one of the pair of the secondheads a baseline and, on the basis of this baseline, obtain acompensation value for a correction of a landing position of a liquidejected by the other one of the pair of the second heads.

Further, preferably, the test pattern is read in by an image reader, anda compensation value for a correction of a liquid ejected by the secondhead is obtained on the basis of the image data which is read in by theimage reader.

In this way, it becomes possible to obtain a compensation value on thebasis of an image of the test pattern, having been acquired by using theimage reader.

Preferably, the compensation value corresponds to a compensation valuefor a correction of a formation position of a dot which, on the medium,needs to be formed at a position coinciding with a position of a targetpixel.

In this way, it becomes possible to appropriately correct a landingposition of a liquid by shifting the formation position of a dot whichneeds to be formed at a position coinciding with a position of a targetpixel.

Embodiments

FIG. 1 is a block diagram illustrating the whole configuration of aprinter 1. FIG. 2 is a schematic side view of the printer 1. When havingreceived print data such as a print job from a computer 100, the printer1 performs control of individual units (a transportation unit 20, a headunit 40, an ultraviolet irradiation unit 80 and a flow path switchingunit 90) through a controller 10, and thereby performs printing ofimages on paper S. Further, a detector group 60 monitors and detectsconditions inside the printer 1, and the controller 10 performs controlof the individual units on the basis of the results of the detectionsconducted by the detector group 60. In addition, a scanner 200 (an imagereader) is also connected to the computer 100.

The controller 10 is a control unit for performing control of theprinter 1. An interface portion 11 is a component for transmitting andreceiving data between the printer 1 and the computer 100 which is anexternal device. A CPU 12 is an arithmetic processing unit forperforming control of the entire printer 1. A memory 13 is a componentfor securing a program storage area, a work area and the like for theCPU 12. The CPU 12 performs control of the individual units through theunit control unit 14 in accordance with the programs stored in thememory 13.

The transportation unit 20 includes an unreeling roll 21, a reeling roll22 and a platen 23. The unreeling roll 21 is a component for feeding amedium, such as the paper S. The unreeling roll 21 is coupled to a motor(not illustrated), and the rotation of the motor is controlled by thecontroller 10. Further, the reeling roll 22 is a component for reelingand collecting a medium, such as the paper S. The reeling roll 22 isalso coupled to a motor (not illustrated), and the rotation of the motoris controlled by the controller 10. Further, the transportation unit 20is provided, between the unreeling roll 21 and the reeling roll 22, withthe platen 23 for supporting the paper S. In this way, images can beformed by ejecting inks onto the paper S which is placed on the platen23 while causing the platen 23 to support the paper S which is fed fromthe unreeling roll 21.

The head unit 40 includes a white ink head unit 41W, a cyan ink headunit 41Cy, a magenta ink head unit 41M, a black ink head unit 41K, ayellow ink head unit 41Y and a clear ink head unit 41Cl.

FIG. 2 illustrates a state where the white ink head unit 41W, the cyanink head unit 41Cy, the magenta ink unit head 41M, the black ink headunit 41K, the yellow ink head unit 41Y and the clear ink head unit 41Clare arranged from the upstream side in a direction in which the paper Sis transported.

Each of these head units 41 which is associated with a corresponding oneof the ink colors is a unit for ejecting ink droplets onto the paper S,and includes a plurality of heads. Each of these heads is provided onits bottom face with a plurality of nozzles through each of which an inkis ejected. This plurality of heads arranged in a zigzag form in each ofthe head units 41 which is associated with a corresponding one of theink colors enables formation of an image whose size in the widthdirection of the paper S is large. Each of the nozzles is provided witha pressure chamber (not illustrated) in which an ink is contained, aswell as a driving element (a piezoelectric element) for causing the inkto be ejected from the pressure chamber by causing a variation of thevolume of the pressure chamber. Further, in this embodiment, an inkejected from each of the head units 41 which is associated with acorresponding one of the ink colors is an ultraviolet hardening type ink(a UV ink).

The ultraviolet irradiation unit 80 includes a plurality of ultravioletirradiation devices 81W, 81Cy, 81M, 81K and 81Y. These ultravioletirradiation units are units each for performing temporal hardening of anink which is already landed on the paper S. Further, an ultravioletirradiation device 81last is provided at a most downstream position. Theultraviolet irradiation unit 81last is a unit for performing fullhardening of an ink which is already landed on the paper S. In addition,the temporal hardening means a process of hardening the surface of anink landed on the paper S to a degree that does not cause the ink to bemixed with an ink whose color is different from that of the ink; whilethe full hardening means a process of hardening an ink landed on thepaper S to a degree that causes the hardening to reach the inside of theink.

Further, the printer 1 includes the flow path switching unit 90. Theflow path switching unit 90, a configuration thereof being describedbelow, is a unit for switching a kind of ink to be fed to clear inkheads 43Cl and white ink heads 43W for each of the clear head Cl and thewhite head W.

FIG. 3 is an explanatory diagram of an arrangement of heads 43 in eachof the head units 41 which is associated with a corresponding one of theink colors. In FIG. 3, there are illustrated the white ink head unit 41W, the cyan ink head unit 41Cy and the clear ink head unit 41Cl amongthe head units 41 for all the ink colors. In FIG. 3, each of the headunits 41 is viewed from its upper direction. Although, actually, thenozzles are hard to be viewed because they are located behind othermembers, here, for the sake of convenience of description, the nozzlesare illustrated such that they become transparently viewable.

Each of the head units 41 includes seven heads 43, and a way ofarranging the heads 43 is common to each of the head units 41. Further,the positions of the nozzles are designed such that, in each of the headunits, the nozzles of one of the heads extend so as to overlap thenozzles of another one of the heads in the width direction of the paperS (a Y direction). Further, each of the heads 43 includes nozzle edges#1 to #360, and a nozzle pitch thereof is 360 dpi. These heads 43 arearranged in a so-called zigzag form, and further, are arranged suchthat, in the width direction of the paper S, a nozzle #359 and a nozzle#360 of one of the heads 43 overlap a nozzle #1 and a nozzle #2 ofanother one of the heads 43 which is adjacent to the one of the head 43,respectively.

In addition, in this embodiment, when all the head units arecollectively referred to, a sign “40” is appended to “head unit”, andwhen a head unit corresponding to a specific ink color is referred to, asign “41” and a sign indicating an ink color corresponding to thespecific ink color are appended to “head unit”. Further, with respect tothe seven heads included in each of the head units 41, when correctivelyreferred to as just heads, a sign “43” is appended to “heads”, andfurther, when heads corresponding to a specific ink color is referredto, a sign indicating an ink color corresponding to the specific inkcolor is appended to the sign “43”. Further, with respect to a certainone of the heads included in each of the head units 41, when a headnumber of the certain head is specified, the certain head is denotedsuch that, additionally, its head number is appended to the signindicating its ink color. Further, in this embodiment, there are somecases where heads included in a certain head unit 41 are referred to bybeing specified by an ink color of the heads, such as “black ink heads43K”.

As described above, the printer 1 is configured so as to eject aplurality of inks, and there occur some cases where, because of errors,such as an error with respect to an attachment position of a certain oneof the heads 43, dots are formed at positions on the paper S which areout of alignment from positions where the dots are originally to belanded. In the case where such misalignments occur among landed dotshaving been printed in a colored ink, amounts of the misalignments canbe recognized with eyes, and can be also recognized by using an image ofthe landed dots, taken by an image reader, such as a scanner. Incontrast, in the case where such misalignments occur among landed dotshaving been printed in a clear ink, amounts of the misalignments arehard to be recognized with eyes because of the feature of the clear ink,and even when an image of the landed dots is taken by an image reader,such as a scanner, it is difficult to recognize the color of the landeddots. Accordingly, it is desired to realize a configuration whichenables correction of landing positions of such a clear ink byappropriately recognizing the landing positions thereof with respect toheads each ejecting the clear ink. A configuration provided in each ofembodiments described below enables correction of landing positions ofthe clear ink by appropriately recognizing the landing positions thereofwith respect to heads each ejecting the clear ink.

FIG. 4 is a flowchart illustrating a compensation value calculationmethod for a clear head. Hereinafter, a compensation value calculationmethod for a clear head will be described with reference to thisflowchart. In this compensation value calculation method, first, fillingrelevant head units with their respective corresponding inks for forminga test pattern is performed (S102).

FIG. 5 is an explanatory diagram of inks with each of which acorresponding one of head units is filled. In FIG. 5, there areillustrated inks with which filling is performed at the time of printingactual images (i.e., inks for use in filling with inks for printing),and inks with which filling is performed at the time of printing a testpattern (i.e., inks for use in filling with inks for testing).

In the filling with inks for printing, the heads 43 of each of the headunits 41 are filled with a corresponding one of the inks for use inprinting. Thus, for example, heads 43W of the white ink head unit 41Ware filled with a white ink. Further, heads 43Cl of the clear ink headunit 41Cl are filled with a clear ink.

Meanwhile, in the filling with inks for testing, the heads 43 of each ofrelevant head units 41 are filled with a corresponding one of inks foruse in forming a test pattern. In this embodiment, when the test patternis formed, each of white ink heads 43W ejects a cyan ink Cy. Thus, whenthe test pattern is formed, each of the white ink heads 43W is filledwith the cyan ink Cy. Further, when the test pattern is formed, each ofclear ink heads 43Cl ejects a yellow ink Y. Thus, when the test patternis formed, each of the clear ink heads 43Cl is filled with the yellowink Y.

FIG. 6A is a first explanatory diagram of ink feeding paths, and FIG. 6Bis a second explanatory diagram of ink feeding paths. FIG. 6Aillustrates feeding paths for inks fed to heads included in a clear inkhead unit. FIG. 6B illustrates feeding paths for inks fed to headsincluded in a white ink head unit. In addition, a mechanism illustratedin FIG. 6A is approximately the same as a mechanism illustrated in FIG.6B except that only a difference exists between ink colors usedtherefor, and thus, operation of the mechanism illustrated in FIG. 6Awill be described and operation of the mechanism illustrated in FIG. 6Bwill be omitted.

FIG. 6A illustrates an yellow ink tank 70Y in which the yellow ink Y isstored; a clear ink tank 70Cl in which a clear ink Cl is stored; yellowink heads 43Y; and the clear ink heads 43Cl.

A first yellow ink feeding tube 92Y_A for feeding the yellow ink Y fromthe yellow ink tank 70Y to the yellow ink heads 43Y is attached to anupper portion of the yellow ink heads 43Y. A clear ink feeding tube 92Cl(corresponding to the second flow path) for feeding the clear ink Clfrom the clear ink tank 70Cl to the clear ink heads 43Cl is attached toan upper portion of the clear ink heads 43Cl. Moreover, a second yellowink feeding tube 92Y_B (corresponding to the first flow path) forfeeding the yellow ink Y from the yellow ink tank 70Y to the clear inkheads 43Cl is attached to another upper portion of the clear ink heads43Cl.

The clear ink feeding tube 92Cl is provided with an electromagneticvalve 91Cl in the mid-flow of the clear ink feeding tube 92Cl itself,and the second yellow ink feeding tube 92Y_B is provided with anelectromagnetic valve 91Y in the mid-flow of the second yellow inkfeeding tube 92Y_B itself. With respect to these electromagnetic valves91Cl and 91Y, their respective opening and closing operations arecontrolled in accordance with signals from the controller 10.

Further, during operation of the foregoing filling with inks forprinting, the electromagnetic valve 91Y is controlled to a closed state;while the electromagnetic valve 91Cl is controlled to an open state, sothat the clear ink heads 43Cl are fed with the clear ink Cl. Meanwhile,during operation of the foregoing filling with inks for testing, theelectromagnetic valve 91Y is controlled to an open state; while theelectromagnetic valve 91Cl is controlled to a closed state, so that theclear ink heads 43Cl are fed with the yellow ink Y.

In this embodiment, when a test pattern is formed, the yellow ink Y isfed to the clear ink heads 43Cl from the yellow ink tank 70Y but,alternatively, an ink tank for test-pattern printing in which a coloredink is contained may be provided in advance, and this colored ink may befed from this ink tank. Moreover, when a test pattern is formed, thecyan ink Cy is fed to the white ink heads 43W from the cyan ink tank70Cy but, alternatively, an ink tank for test-pattern printing in whicha colored ink is contained may be provided in advance, and this coloredink may be fed from this ink tank.

In addition, when switching of these inks is performed, it is desirableto perform operation of ejecting all inks remaining inside the heads(for example, flushing operation or the like). In this way, when thefilling with inks for testing is performed, it is possible to feed theyellow ink Y to the clear ink heads 43Cl and feed the cyan ink Cy to thewhite ink heads 43W.

Next, printing of a test pattern is performed (S104).

FIG. 7 is a schematic explanatory diagram of a test pattern. In FIG. 7,the white ink head unit 41W, the cyan ink head unit 41Cy and the clearink head unit 41Cl are partially illustrated. Further, a test patternhaving been formed by these head units is illustrated.

This test pattern is composed of a test pattern t (Cy) formed by thecyan ink head unit 41Cy; a test pattern t (W) formed by the white inkhead unit 41W; and a test pattern t (Cl) formed by the clear ink headunit 41Cl. Each of these three kinds of test patterns includes aplurality of ruled lines L. Further, each of the ruled lines L isdenoted by two signs appended to a sign “L”, a first one being a signindicating an ink color of one of the head units which includes a headhaving formed the relevant ruled line L, a second one being a signindicating a serial number of the head within the one of the head units.For example, “L (Cy1)” indicates a ruled line having been formed by ahead 43Cy1 which is a 1st one of cyan ink heads 43Cy. Further, forexample, “L (Cl3)” indicates a ruled line having been formed by a head43Cl3 which is a 3rd one of clear ink heads 43Cl. As shown in FIG. 7,ruled lines of every two adjacent heads are formed so as to be distancedfrom each other in the transportation direction.

FIG. 8 is a first explanatory diagram of a test pattern. In FIG. 8,there are illustrated a cyan ink head 43Cy4 and a clear ink head 43Cl4.In FIG. 8, among a plurality of ruled lines included in a test pattern,a ruled line L (Cy4) having been printed by the illustrated cyan inkhead 43Cy4 and a ruled line L (Cl4) having been printed by theillustrated clear ink head 43Cl4 are illustrated. In addition, at thistime, this ruled line L (Cl4) becomes visible because an ink ejectedfrom the clear ink head 43Cl4 is the yellow ink Y.

Further, in FIG. 8, a theoretical position indication line correspondingto the ruled line L (Cl4) having been printed by the clear ink head43Cl4, the theoretical position indication line being distanced from theruled line L (Cy4) having been printed by the cyan ink head 43Cy4 by atheoretical distance, is denoted by an alternate long and short dashline. Originally, the ruled line L (Cl4) is a line to be formed on thetheoretical position indication line. Thus, an amount of a misalignmentof the ruled line L (Cl4) relative the theoretical position indicationline corresponds to an error.

Here, an amount of a misalignment of the ruled line L (Cl4) having beenprinted by the clear ink head 43Cl4 is obtained by making the ruled lineL (Cy4) having been printed by the cyan ink head 43Cy4 a baseline, andon the basis of this obtained amount of a misalignment, a compensationvalue by which landing positions of dots formed by the clear ink head43Cl4 are to be corrected is obtained.

Next, compensation value calculation processing is performed (S106). Inthe correction of dot landing positions in this embodiment, shifting ofpixel data, which will be described below, is performed, and thecompensation value is a value indicating the number of pixels equivalentto a shift amount by which the pixel data is to be shifted.

The foregoing printed test pattern (FIG. 7) is read in by the scanner200 prior to beginning of the compensation value calculation processing(S106). Further, on the basis an image generated from the read-in testpattern, the positions of ruled lines included in the test pattern areidentified. In addition, the identification of the positions of theruled lines included in the test pattern may be performed by not usingthe scanner 200 but simply measuring the printed ruled lines.

FIG. 9 is an explanatory diagram of an error of a ruled line printed bya clear head. In FIG. 9, a theoretical position indication line handledas a baseline is denoted by an alternate long and short dash line.Further, in FIG. 9, the ruled line L (Cl4) having been printed by theclear ink head 43Cl4 is illustrated.

A ruled line is printed by ejecting an ink through each of all nozzlesof a head. That is, a ruled line is printed by ejecting an ink througheach of nozzles #1 to #360 of a head. A distance from the nozzle #1 upto the nozzle #360 is known from a design specification. Thus, from arelation with the distance between these two nozzles, it is possible torecognize by which one of the nozzles each of dots existing on the ruledline has been formed.

Here, as shown in FIG. 9, for example, the positions of dots having beenformed by the nozzle #10 and the nozzle #350 are identified. At thistime, a method for obtaining a compensation value for a correction ofthe position of a dot formed by a nozzle of a certain nozzle number isconsidered. As described above, in this embodiment, it is supposed thatthe compensation value is a shift amount by which pixel data is to beshifted. Here, this pixel data is data for specifying, for each ofpixels on a medium, which size of a dot is to be formed and which kindof an ink to be used. A method for shifting the pixel data will bedescribed below.

In FIG. 9, a misalignment value x of a dot having been formed by anozzle of a certain nozzle number is illustrated. In FIG. 9, withrespect to this misalignment value x, a ratio relationship describedbelow is satisfied. In addition, in FIG. 9, X1, X2 and Y1 are valueswhich can be measured on the basis of image data having been read in bythe scanner 200.

(X1+X2):Y1=(x+X1):(target nozzle number/340)×Y1

The misalignment amount x can be obtained from this relationship.

In this embodiment, a pixel pitch in the transportation direction is 360dpi. Thus, the size of a pixel becomes approximately 0.071 millimeters.Accordingly, a compensation value (the number of pixels to be shifted)can be obtained by x/0.071. Such a compensation value can be obtainedfor each of all the nozzles in such a way as described above.

FIG. 10 is a second explanatory diagram of a test pattern. In FIG. 10,two adjacent clear ink heads 43Cl4 and 43Cl5 are illustrated. Further,in FIG. 10, ruled lines having been printed by these clear ink heads43Cl4 and 43Cl5 are illustrated. In addition, when a test pattern isformed, the yellow ink Y is fed to the clear ink heads 43Cl4 and 43Cl5,and thus, these ruled lines become visible in yellow.

The ruled lines corresponding to these adjacent heads are printed so asto be distanced from each other by a given theoretical distance in thetransportation direction. In FIG. 10, a theoretical position indicationline corresponding to the ruled line L (Cl5) having been printed by theclear ink head 43Cl5, the theoretical position indication line beingdistanced from the ruled line L (Cl4) having been printed by theadjacent clear ink head 43Cl4 by a theoretical distance, is denoted byan alternate long and short dash line. Originally, the ruled line L(Cl5) is a line to be formed on the theoretical position indication linedenoted by the alternate long and short dash line. Thus, an amount of amisalignment of the ruled line L (Cl5) relative the theoretical positionindication line denoted by the alternate long and short dash linecorresponds to an error.

Here, an amount of a misalignment of the ruled line L (Cl5) is obtainedby making the ruled line L (Cy4) a baseline, and on the basis of thisobtained amount of a misalignment, a compensation value by which landingpositions of dots formed by the clear ink head 43CL5 are to be correctedis obtained.

As described above, in FIG. 10, a theoretical position indication lineis denoted by an alternate long and short dash line, and obtaining anerror relative to this alternate long and short dash line is common tothe foregoing case of FIG. 8. For this reason, in the case of FIG. 10,as a result, it becomes possible to obtain a compensation value in thesame method as that for obtaining a compensation value, having beendescribed by using FIG. 9. Accordingly, the method for obtaining acompensation value is omitted here.

Further, the method for calculating the misalignment amount x, havingbeen described by using FIGS. 8 to 10, can be applied to ruled lines L(W) having been printed by the white ink heads 43W in the same way asdescribed above. That is, a compensation value by which landingpositions of dots formed by a white ink head 43W4 are to be correctedcan be obtained by obtaining an amount of a misalignment of a ruled lineL (W4) having been printed by the white ink head 43W4 while making aruled line L (Cy4) having been printed by the cyan ink head 43Cy4 abaseline. Further, with respect to the white ink head 43W4 and a whiteink head 43W5 which are adjacent to each other, an amount of amisalignment of a ruled line L (W5) is obtained by making the ruled lineL (W4) a baseline, and this obtained amount of a misalignment of theruled line L (W5) makes it possible to obtain a compensation value bywhich landing positions of dots formed by the white ink head 43W5 are tobe corrected.

The compensation values having been obtained in such a way as describedabove are stored in the memory 13 of the printer 1 (S108). Further, as aresult, when printing is carried out, relevant dot formation positionsare corrected by using the stored compensation values.

FIG. 11 is a flowchart illustrating printing processing. In the casewhere a test pattern has been printed immediately before beginning ofprinting processing, each of the clear ink heads 43Cl must be filledwith the yellow ink Y and each of the white ink heads 43W must be filledwith the cyan ink Cy. Meanwhile, before actually performing printing ofimages, each of the heads needs to be filled with a corresponding one ofthe inks for use in printing. Thus, filling the heads 43 included ineach of the head units 41 with a corresponding ink for printing isperformed (S202).

In addition, in the case where this printing processing has beenperformed immediately before beginning of printing processing and eachof the heads 43 is already filled with a corresponding ink for printing,the processing in step S202 can be omitted.

Next, pixel data is created (S204). This creation of pixel data can becarried out by utilizing a printer driver installed in the computer 100.The pixel data is data which specifies, for each of pixels on a medium,an ink color and a dot size of an ink to be landed. Thus, the printerdriver creates the pixel data by obtaining, for each of pixels on amedium, the ink color and the dot size of an ink to be landed, on thebasis of image data given by an application.

Next, pixel data shifting processing is performed (S206).

FIG. 12 is an explanatory diagram of pixel data shifting processing.This pixel data shifting processing is processing for interchangingpixel data so as to cause the positions of relevant pieces of pixel datato be shifted, on the basis of obtained compensation values. In theupper portion of FIG. 12, pixel data before beginning of image datashifting processing is illustrated, and in the lower portion of FIG. 12,pixel data after completion of pixel data shifting processing isillustrated.

Pixels on the paper S form rows of pixels aligning in the direction inwhich the paper S is transported. One of the rows of pixels correspondsto, for each of the head units, one of the nozzles included in one ofthe heads. In the upper portion of FIG. 12, as an example, a row ofpixels, corresponding to a nozzle #270 of the clear ink head 43Cl5, isillustrated. Each of variables a1 to a7, which are illustrated so as tobe associated with their respective corresponding pixels, includes anink color and a dot size of a dot to be formed on its correspondingpixel.

For example, it is supposed that the foregoing misalignment amount xcorresponding to the nozzle #270 of the clear ink head 43Cl5 is 0.25millimeters. In this embodiment, the size of a pixel is 0.071millimeters, and thus, it can be understood that three pieces of pixeldata whose number is obtained by approximately dividing “0.25” by“0.071” need to be shifted. That is, a value “3” representing threepixels is stored as a compensation value corresponding to the nozzle#270 of the clear ink head 43Cl5. According to FIG. 9 described above,it can be understood that shifting of pixel data to the positive side inan X direction results in forming corresponding dots at their respectivecorrect positions. Thus, as shown in the lower portion of FIG. 12, thepixel data is reconfigured such that the individual pieces of pixel dataare shifted to the right-hand side by three pixels (S206).

After the shifting processing on pieces of pixel data with respect tonozzles corresponding to each of all the pixels has been completed inthe same way as described above, printing is carried out on the basis ofresultant corrected pixel data (S208). In this way, each of dots can beformed on a corresponding corrected position.

According to this embodiment, when forming a test pattern, a colored inkis fed to each of clear ink heads which ejects a clear ink, and thus,each of the clear ink heads can form a corresponding colored ruled line.Further, visible ruled lines can be formed, and thus, through thesevisible ruled lines, it is possible to appropriately obtain compensationvalues for corrections of landing positions. Further, it is possible toperform printing on the basis of these obtained compensation values.

In addition, in this embodiment, the number of pixels to be shifted ishandled as a compensation value, but in the case where ejection timingis adjusted in the correction of a landing position of an ink, an amountof shifting of ejection timing may be handled as the compensation value.

Further, a correction method for ink landing positions is not limited tothe aforementioned method. If a correction method for ink landingpositions includes processing for, when forming a test pattern, forminga colored pattern by feeding a colored ink to clear ink heads each forejecting a clear ink, and obtaining compensation values on the basis ofthis colored pattern, this correction method is included in the scope ofthis embodiment.

Other Embodiments

In the aforementioned embodiment, the description has been made on theprinter 1, but the invention is not limited to this and can be alsoembodied in liquid ejection apparatuses each injecting or ejecting afluid material other than ink, such as a liquid, a liquid material inwhich particles of functional materials are dispersed, or a fluidmaterial such as a gel material. The same technologies as those of theaforementioned embodiment may be applied to various devices to which inkjet technologies are applied, such as color filter manufacturingdevices, dyeing devices, micro fabrication devices, semiconductormanufacturing devices, surface treatment devices, three-dimensionalmodeling devices, gas evaporation devices, organic EL manufacturingdevices (particularly, polymer EL manufacturing devices), displaymanufacturing devices, coating devices, and DNA chip manufacturingdevices. Further, not only the devices themselves but also methods forrealizing target services provided by the devices and manufacturingmethods for target products of the devises are also included within thescope of the application of the invention.

The aforementioned embodiments are intended to make it easy tounderstand the invention and are not intended to limit theinterpretation of the invention. The invention may be modified andimproved without departing from the spirit of the invention, andobviously, equivalents thereof are included in the scope of theinvention.

Regarding Heads

In the aforementioned embodiment, inks are ejected by usingpiezoelectric elements. However, methods of ejecting liquids are notlimited to this method. Other methods, such as a method of generatingbubbles inside a nozzle by means of heating, may be employed.

The entire disclosure of Japanese Patent Application No. 2013-071619,filed Mar. 29, 2013 is expressly incorporated by reference herein.

What is claimed is:
 1. A method for calculating a compensation value foruse in a correction of a liquid landing position in a liquid ejectiondevice provided with a first head for ejecting a first colored liquidand a second head for ejecting a transparent liquid, the methodcomprising: when forming a test pattern on a medium, forming the testpattern by feeding the first colored liquid to the second head andcausing the second head to eject the first colored liquid, and obtaininga compensation value for a correction of a landing position of a liquidejected by the second head on the basis of the test pattern formed onthe medium.
 2. The method for calculating a compensation value,according to claim 1, wherein the liquid ejection device is providedwith a third head for ejecting a white liquid, and wherein, when thetest pattern is formed, the test pattern is formed by feeding a secondcolored liquid to the third head and causing the third head to eject thesecond colored liquid, and a compensation value for a correction of alanding position of a liquid ejected by the third head is obtained onthe basis of the test pattern formed on the medium.
 3. The method forcalculating a compensation value, according to claim 2, wherein, whenthe test pattern is formed, a color of the first colored liquid fed tothe second head is different from a color of the second colored liquidfed to the third head.
 4. The method for calculating a compensationvalue, according to claim 1, wherein the liquid ejection device isprovided with a first container for storing therein the first coloredliquid and a first flow path for feeding the first colored liquid to thesecond head from the first container and a second container for storingtherein the transparent liquid and a second flow path for feeding thetransparent liquid to the second head from the second container, andwherein, when the first colored liquid is fed to the second head, thefirst colored liquid is fed to the second head through the first flowpath, and feeding of the transparent liquid to the second head throughthe second flow path is brought to a stop.
 5. The method for calculatinga compensation value, according to claim 1, wherein the liquid ejectiondevice is provided with a fourth head for ejecting a colored liquidwhose color is different from a color of the first colored liquid, andwherein, when the test pattern is formed, the fourth head is caused toform a first pattern, the second head is caused to form a secondpattern, and a compensation value for a correction of a landing positionof a liquid ejected by the second head is obtained on the basis of thefirst pattern and the second pattern.
 6. The method for calculating acompensation value, according to claim 1, wherein the liquid ejectiondevice is provided with a plurality of second heads; wherein theplurality of second heads are arranged such that a nozzle row of any oneof the second heads extends so as to overlap at least part of a nozzlerow of at least one of the other second heads in a directionintersecting with a direction in which the medium is transported, andwherein a compensation value for a correction of a landing position of aliquid ejected by any one of the second heads is equivalent to acompensation value which is obtained such that, for any two of thesecond heads, a landing position of a liquid ejected by one of the twosecond heads is made a baseline, and on the basis of the baseline, acompensation value for a correction of a landing position of a liquidejected by the other one of the two of the second heads is obtained. 7.The method for calculating a compensation value, according to claim 1,wherein the test pattern is read in by an image reader, and acompensation value for a correction of a liquid ejected by the secondhead is obtained on the basis of the image data which is read in by theimage reader.
 8. The method for calculating a compensation value,according to claim 1, wherein the compensation value corresponds to acompensation value for a correction of a formation position of a dotwhich, on the medium, needs to be formed at a position coinciding with aposition of a target pixel.